Take-home carbamide peroxide gel. Glycol based formulation delivers excellent results with minimum dehydration. The 21% concentration should only be used for patients with no history of thermal sensitivity, while the 16% gel should be dispensed to those prone to sensitivity. Gel is applied 1 to 2 hours daily, depending on the concentration, for at least 2 weeks (each patient treatment consists of six 3cc syringes).